1. Field of the Invention
The present invention relates to a shutheight adjustment mechanism for use in press machines, and, more particularly, to a method and apparatus for modifying the spatial relationship between the parts of the shutheight adjustment mechanism such as the threaded nut and screw members by inducing a deformation activity therein which is sufficient to displace the threaded portions into an interlocking engagement that eliminates the free clearances therebetween.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction including a frame having a crown and bed portion and a slide supported within the frame for reciprocating movement toward and away from the bed. The slide is driven by a crankshaft having a connecting arm coupled to the slide. These mechanical presses are widely used for a variety of workpiece operations employing a diverse array of die sets, with the press machine varying substantially in size and available tonnage depending upon its intended use. The availability of a diverse selection of die sets for installation into the press machines requires an adjustment capability that tailors the shutheight dimension to the particular configuration of press machine and die assembly.
One conventional press arrangement employs a slide configured for connection to the crankshaft by a connecting rod that is adjustable in length or which is connected to another device such as a connection screw that is adjustable in its spatial separation from the slide, thereby permitting adjustments to be made to the shutheight dimension in order to accommodate various die sets. Adjustment mechanisms of the type employing an adjustable connecting rod or connection screw have typically been arranged such that the individual working parts are disposed within the slide, requiring that any shutheight adjustments be made only through changes in the position of the slide relative to the bed. Alternatively, the bed portion or bolster assembly of the press may have its position adjusted relative to the slide so as to adjust the shutheight therebetween. Regardless of the mode of shutheight adjustment, the slide is generally guided on the uprights of the press frame extending between the crown and bed so that the parts of the die set remain in accurate registration as the slide reciprocates.
One conventional adjustment mechanism employs a plurality of connection screw assemblies configured within the slide and actuated simultaneously by means of a worm-gear arrangement, which is driven either manually or by means of an operator controlled motor. This arrangement effectuates a change in the shutheight by changing the position of the slide relative to each of the connection screws. As known, the manufacture and assembly of any form of shutheight adjustment mechanism requires the development of various spatial clearances between the discrete parts of the mechanism. Additionally, it is necessary to implement various working tolerances between the connected portions of the press, specifically the connections that couple the shutheight adjustment mechanism to the slide or bolster. Proper formation of these clearances and tolerances allows the worm gear, adjustment nuts, and connection screws, for example, to be rotated and otherwise moved so that the adjustment mechanism may be suitably operated.
However, the existence of such clearances and tolerances present various difficulties in accurately controlling press shutheight and in reproducing a constant bottom-dead-center operating range since the clearances permit small but adverse displacements of the adjustment mechanism parts and the attached slide or bolster beyond their normal operating range under certain load conditions. Current problems with shutheight adjustment mechanisms include the transfer of punching and snap through loads through the adjustment mechanism during press operation. A press load is the load created by the mechanical press when the slide is urging its associated die member into contact with the workpiece. When the workpiece fractures in the die, the slide attempts to rapidly accelerate downward, which corresponds to the snap through action. This snap through load is comprised mainly of the downward acceleration and the downward slide crank inertial acceleration of the die and slide combination. The failure to implement measures aimed at counteracting such snap through loads or retarding such snap through action may cause an unwanted change in the shutheight and lead to excessive die penetration beyond its normal operating range.
The clearances also prevent the uniform transmission of pressure loads throughout the press machine since certain force components may be communicated more or less extensively within the machine relative to other force components depending upon the degree that the force-transmitting parts shift within the clearances. This uneven distribution of forces may cause particular parts to experience concentrated impact forces leading to breakdown or failure. Again, the clearances between the parts permit the shutheight to variably change during operation of the press, resulting in workpieces that may not meet design specifications.
According to the present invention there is provided a method and apparatus for substantially eliminating the free clearances present within shutheight adjustment mechanisms that are configured for use in press machines. One illustrative arrangement of the shutheight adjustment mechanism includes a male threaded member provided in the form of a screw that threadedly engages a female threaded member provided in the form of an adjustment nut disposed about the screw. Relative rotation between the screw and adjustment nut effectuates a change in the shutheight. A clearance space is defined between respective threaded portions of the screw and adjustment nut to enable actuation of the shutheight adjustment mechanism, e.g., rotation of the adjustment nut relative to the screw.
An apparatus is provided according to the present invention to induce a deformation activity in at least one of the screw and adjustment nut that is sufficient to enable these parts to be brought into substantial interlocking engagement with one another at their respective threaded portions. This locking condition is particularly characterized by the substantial elimination of the original free clearances existing between the threaded portions of the screw and adjustment nut, thereby preventing relative rotation between the parts and effectively opposing any occurrence of snap through or other causes of excessive die penetration. This interlocking engagement is produced in one embodiment by a hydraulic assembly that directs a pressurized fluid against an outer periphery of the adjustment nut to effectively exert a compressive action upon the adjustment nut that radially displaces the threaded portion thereof into locked engagement with the threaded portion of the screw. The deformation activity in the adjustment nut may be sufficiently ordered to induce further an accompanying elongation thereof along its axial dimension to close out any clearance spaces formed adjacent the axial end surfaces of the adjustment nut. In another embodiment, a hydraulic assembly is arranged to hydraulically pressurize an interior space of the screw to effectively exert an expansive action upon the screw that radially displaces the threaded portion thereof into locked engagement with the threaded portion of the adjustment nut. The induced deformation activity present in both the screw and adjustment nut is preferably reversible and remains intact by maintaining the holding pressure upon the affected part until it is desired to restore the shutheight adjustment mechanism to an actuatable condition.
The invention, in one form thereof, comprises a press machine having a frame structure with a crown and a bed; a slide guided by the frame structure for operative reciprocating movement in opposed relation to the bed; a drive assembly attached to the frame structure for operatively reciprocating the slide; a bolster assembly mounted to the bed; and a shutheight adjustment mechanism configured within the press machine and arranged to controllably adjust the press shutheight between the slide and the bed. The shutheight adjustment mechanism includes a male threaded member threadedly engaging a female threaded member wherein at least one of the threaded members is rotatable relative to the other of the threaded members to change the press shutheight. The shutheight adjustment mechanism includes at least one clearance space defined between respective threaded portions of the male threaded member and the female threaded member. The press machine further comprises a means for inducing a deformation activity in at least one of the male threaded member and the female threaded member in a manner sufficient to effectuate a substantial interlocking engagement between the respective threaded portions of the male threaded member and the female threaded member. The male threaded member preferably includes a screw, while the female threaded member preferably includes an adjustment nut disposed about the screw. The interlocking engagement between the nut and screw is preferably characterized by a substantial elimination of the free clearance spaces otherwise associated with the threaded portions thereof.
The means for inducing such deformation activity further includes a hydraulic assembly arranged to compress the female threaded member by applying pressurized fluid along a periphery thereof and/or expand the male threaded member by hydraulically pressurizing an interior space thereof. The deformation activity generated in the female threaded member is preferably sufficient to further induce an accompanying elongation of the female threaded member along an axial dimension thereof which is sufficient to substantially close out at least one clearance space defined adjacent a respective axial end surface of the female threaded member.
The hydraulic assembly is arranged further to selectively direct pressurized fluid against one axial end surface of the female threaded member to effectively displace another axial end surface of the female threaded member in a manner sufficient to substantially close out a clearance space defined adjacent the another axial end surface.
The shutheight adjustment mechanism is attached to a one of the slide and the bolster assembly. Additionally, the shutheight adjustment mechanism may be arranged further to enable an adjustment-in-motion operability.
The drive assembly of the press machine further includes, in one illustrative combination thereof, a crankshaft; a plurality of connection assemblies each arranged to couple the crankshaft to the slide, wherein each one of the connection assemblies respectively includes a wrist pin and an associated connecting rod pivatingly connected to the wrist pin and defining therewith at least one clearance space therebetween; and a second means for inducing a deformation activity in at least one of the wrist pins which is sufficient to displace an outer periphery of the at least one wrist pin to substantially close out at least one of the at least one clearance space associated therewith.
The second means for inducing a deformation activity further comprises a hydraulic assembly arranged to hydraulically pressurize an interior space of the at least one wrist pin to effectuate the respective deformation activity therein.
The invention, in another form thereof, comprises a press machine including, in combination, a frame structure with a crown and a bed; a slide guided by the frame structure for operative reciprocating movement in opposed relation to the bed; a drive assembly attached to the frame structure for operatively reciprocating the slide; a bolster assembly mounted to the bed; and a shutheight adjustment mechanism configured within the press machine and arranged to controllably adjust the press shutheight between the slide and the bed. The shutheight adjustment mechanism comprises a male threaded member threadedly engaging a female threaded member wherein at least one of the threaded members is rotatable relative to the other of the threaded members to thereby change the press shutheight. The shutheight adjustment mechanism operatively includes at least one clearance space defined between respective threaded portions of the male threaded member and the female threaded member. The press machine further comprises a hydraulic assembly arranged to operatively perform at least one of (i) compressing at least in part the female threaded member by applying pressurized fluid along a periphery thereof in a manner sufficient to bring the respective threaded portion thereof into interlocking engagement with the male threaded member at the respective threaded portion thereof, and (ii) expanding at least in part the male threaded member by hydraulically pressurizing an interior space thereof in a manner sufficient to bring the respective threaded portion thereof into interlocking engagement with the female threaded member at the respective threaded portion thereof.
The compression of the female threaded member is associated with the presence of a reversible deformation activity occurring therein, while the expansion of the male threaded member is likewise associated with the presence of a reversible deformation activity occurring therein. The interlocking engagement between the male threaded member and the female threaded member is preferably characterized by a substantial elimination of a clearance space associated with respective threaded portions of the male threaded member and the female threaded member which are disposed in such interlocking engagement.
The deformation activity generated in the female threaded member is preferably sufficient to further induce an accompanying elongation of the female threaded member along an axial dimension thereof which is sufficient to substantially close out at least one axial clearance space defined adjacent a respective axial end surface of the female threaded member.
The hydraulic assembly is arranged further to selectively direct pressurized fluid against one axial end surface of the female threaded member to effectively displace another axial end surface of the female threaded member in a manner sufficient to substantially close out an axial clearance space defined adjacent the another axial end surface.
The invention, in another form thereof, comprises a press machine comprising, in combination, a frame structure with a crown and a bed; a slide guided by the frame structure for operative reciprocating movement in opposed relation to the bed; a drive assembly attached to the frame structure for operatively reciprocating the slide; a bolster assembly mounted to the bed; and a shutheight adjustment mechanism configured within the press machine and arranged to controllably adjust the press shutheight between the slide and the bed. The shutheight adjustment mechanism comprises a male threaded member threadedly engaging a female threaded member wherein at least one of the threaded members is rotatable relative to the other of the threaded members to thereby change the press shutheight. The shutheight adjustment mechanism operatively includes at least one clearance space defined between respective threaded portions of the male threaded member and the female threaded member. The press machine further comprises an actuating assembly operatively associated with the shutheight adjustment mechanism and arranged to effectuate a substantial interlocking engagement between the respective threaded portions of the male threaded member and the female threaded member by (i) compressing at least in part the female threaded member and/or (ii) expanding at least in part the male threaded member.
The actuating assembly further includes a hydraulic assembly that is arranged to (i) apply a pressurized fluid along a periphery of the female threaded member to exert a compressive influence thereon and/or (ii) hydraulically pressurize an interior space formed in the male threaded member to exert an expansive influence thereon. The interlocking engagement between the male threaded member and the female threaded member is preferably characterized by a substantial elimination of a clearance space associated with respective threaded portions of the male threaded member and the female threaded member which are disposed in such interlocking engagement. The male threaded member preferably includes a screw, while the female threaded member preferably includes an adjustment nut disposed about the screw. Additionally, the shutheight adjustment mechanism is attached to a one of the slide and the bolster assembly.
The compression of the female threaded member is preferably sufficient to further induce an accompanying elongation of the female threaded member along an axial dimension thereof which is sufficient to substantially close out at least one clearance space defined adjacent a respective axial end surface of the female threaded member.
The invention, in another form thereof, comprises a method of adjusting the shutheight in a press machine, wherein such press machine comprises a frame structure with a crown and a bed, a slide guided by the frame structure for operative reciprocating movement in opposed relation to the bed, a drive assembly attached to the frame structure for operatively reciprocating the slide, and a bolster assembly mounted to the bed. In accordance with such shutheight adjustment method, there is provided a shutheight adjustment mechanism configured within the press machine and arranged to controllably adjust the press shutheight between the slide and the bed. The shutheight adjustment mechanism comprises a male threaded member threadedly engaging a female threaded member, wherein at least one of the threaded members is rotatable relative to the other of the threaded members to thereby change the press shutheight. The shutheight adjustment mechanism operatively includes at least one clearance space defined between respective threaded portions of the male threaded member and the female threaded member.
When a locking mode is desired for the shutheight adjustment mechanism, a deformation activity is induced in at least one of the male threaded member and the female threaded member in a manner sufficient to effectuate a substantial interlocking engagement between the respective threaded portions of the male threaded member and the female threaded member. This inducement of the deformation activity is associated with a holding influence acting upon the affected threaded member that is effective in adjustably continuously maintaining the interlocking engagement.
When an adjustment mode is desired for the shutheight adjustment mechanism and the locking mode has been enabled, the holding influence is first reduced to a level sufficient to accommodate operative rotational activity between the male threaded member and the female threaded member. Next, the shutheight adjustment mechanism may be actuated to controllably change the shutheight. The holding influence is preferably restored to a level sufficient to effectuate and thereby reinstate the locking mode. When an adjustment mode is desired for the shutheight adjustment mechanism and the locking mode is not in use, the shutheight adjustment mechanism is actuated in a conventional manner to controllably change the shutheight.
Inducing a deformation activity in at least one of the male threaded member and the female threaded member respectively comprises the steps of (a) directing pressurized fluid against an outer periphery of the female threaded member to generate deformation activity therein, and (b) hydraulically pressurizing an interior space of the male threaded member to generate deformation activity therein. Accordingly, a reduction in the holding influence may be accomplished respectively by (a) reducing the pressurization level of fluid directed against the outer periphery of the female threaded member, and (b) reducing the hydraulic pressurization level within the interior space of the male threaded member.
The interlocking engagement between the male threaded member and the female threaded member is preferably characterized by a substantial elimination of a clearance space associated with respective threaded portions of the male threaded member and the female threaded member which are disposed in such interlocking engagement.
The present invention, in yet another form thereof, comprises a method of adjusting the shutheight in a press machine having a frame structure with a crown and a bed, a slide guided by the frame structure for operative reciprocating movement in opposed relation to the bed, a drive assembly attached to the frame structure for operatively reciprocating the slide, and a bolster assembly mounted to the bed. In accordance with such shutheight adjustment method, there is first provided a shutheight adjustment mechanism configured within the press machine and arranged to controllably adjust the press shutheight between the slide and the bed. The shutheight adjustment mechanism comprises a male threaded member threadedly engaging a female threaded member, wherein at least one of the threaded members is rotatable relative to the other of the threaded members to thereby change the press shutheight. The shutheight adjustment mechanism operatively includes at least one free clearance space defined between respective threaded portions of the male threaded member and the female threaded member.
When a locking mode is desired for the shutheight adjustment mechanism, a substantial interlocking engagement is effectuated between the respective threaded portions of the male threaded member and the female threaded member by (i) compressing at least in part the female threaded member and/or (ii) expanding at least in part the male threaded member. When an adjustment mode is desired for the shutheight adjustment mechanism and such locking mode has been enabled, there is performed a reduction in at least one of (i) the compression of the female threaded member and (ii) the expansion of the male threaded member, to a level sufficient to accommodate actuation of the shutheight adjustment mechanism. After xe2x80x9cunlockingxe2x80x9d the shutheight adjustment mechanism, the relevant parts are actuated to controllably change the shutheight. It is then preferable to restore at least one of (i) the compression of the female threaded member and (ii) the expansion of the male threaded member, to a level sufficient to effectuate and thereby reinstate the locking mode. When an adjustment mode is desired for the shutheight adjustment mechanism and the locking mode has not been engaged, the shutheight is simply changed by actuating the shutheight adjustment mechanism in a conventional manner.
In accordance with a preferred implementation of the shutheight adjustment method, the compression of the female threaded member includes directing a pressurized fluid against an outer periphery thereof, while the expansion of the male threaded member includes hydraulically pressurizing an interior space formed therein. The interlocking engagement between the male threaded member and the female threaded member is preferably characterized by a substantial elimination of a clearance space associated with respective threaded portions of the male threaded member and the female threaded member which are disposed in such interlocking engagement.
One advantage of the present invention is that the individual parts of the shutheight adjustment mechanism may be selectively locked together when the mechanism is otherwise not actuated, thereby eliminating during the pendency of this locking state the free clearances that pose problems of die penetration for the press machine.
Another advantage of the present invention is that the shutheight adjustment mechanism may be variably operated in a selected one of a locking condition, an adjustment condition, and a damping condition (i.e., the free clearances are filled with fluid to form a load-supporting pressure squeeze-film) depending upon the current operating environment, load characteristics, and other working parameters.
A further advantage of the present invention is that by controllably eliminating the free clearances located at the threaded portions of the adjustment nut and screw, at the axial end surfaces of the adjustment nut, and between the wrist pin and connecting rod of the slide connection assembly, it is now possible to reduce the snap through effect and thereby eliminate or greatly diminish the die penetration problem.
A further advantage of the present invention is that the functionality of eliminating the free clearances by compressing the adjustment nut and/or expanding the screw is compatible with, and may be seamlessly incorporated into, any of various shutheight adjustment mechanisms having operational features such as adjustment-in-motion and a quick-access hydraulic pressurization apparatus.
A yet further advantage of the present invention is that the bottom-dead-center level associated with the slide operating range is reliably reproducible and repeatable.